/*
Copyright (C) 1997-2001 Id Software, Inc.

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  

See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/
/* Modifications
   Copyright 2003-2004 Bytonic Software
   Copyright 2010 Google Inc.
*/
package jake2.qcommon;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;


public class MD4  implements Cloneable {
	// MD4 specific object variables
	//...........................................................................

	/**
	 * The size in bytes of the input block to the tranformation algorithm.
	 */
	private static final int BLOCK_LENGTH = 64; //    = 512 / 8;

	/**
	 * 4 32-bit words (interim result)
	 */
	private int[] context = new int[4];

	/**
	 * Number of bytes processed so far mod. 2 power of 64.
	 */
	private long count;

	/**
	 * 512 bits input buffer = 16 x 32-bit words holds until reaches 512 bits.
	 */
	private byte[] buffer = new byte[BLOCK_LENGTH];

	/**
	 * 512 bits work buffer = 16 x 32-bit words
	 */
	private int[] X = new int[16];

	// Constructors
	//...........................................................................

	public MD4() {
		
		engineReset();
	}

	/**
	 *    This constructor is here to implement cloneability of this class.
	 */
	private MD4(MD4 md) {
		this();
		context = new int[md.context.length];
		System.arraycopy(md.context, 0, context, 0, context.length);
		buffer = new byte[md.buffer.length];
		System.arraycopy(md.buffer, 0, buffer, 0, buffer.length);
		count = md.count;
	}

	// Cloneable method implementation
	//...........................................................................

	/**
	 * Returns a copy of this MD object.
	 */
	public Object clone() {
		return new MD4(this);
	}

	// JCE methods
	//...........................................................................

	/**
	 * Resets this object disregarding any temporary data present at the
	 * time of the invocation of this call.
	 */
	public void engineReset() {
		// initial values of MD4 i.e. A, B, C, D
		// as per rfc-1320; they are low-order byte first
		context[0] = 0x67452301;
		context[1] = 0xEFCDAB89;
		context[2] = 0x98BADCFE;
		context[3] = 0x10325476;
		count = 0L;
		for (int i = 0; i < BLOCK_LENGTH; i++)
			buffer[i] = 0;
	}

	/**
	 * Continues an MD4 message digest using the input byte.
	 */
	public void engineUpdate(byte b) {
		// compute number of bytes still unhashed; ie. present in buffer
		int i = (int) (count % BLOCK_LENGTH);
		count++; // update number of bytes
		buffer[i] = b;
		if (i == BLOCK_LENGTH - 1)
			transform(buffer, 0);
	}

	/**
	 * MD4 block update operation.
	 * <p>
	 * Continues an MD4 message digest operation, by filling the buffer,
	 * transform(ing) data in 512-bit message block(s), updating the variables
	 * context and count, and leaving (buffering) the remaining bytes in buffer
	 * for the next update or finish.
	 *
	 * @param    input    input block
	 * @param    offset    start of meaningful bytes in input
	 * @param    len        count of bytes in input block to consider
	 */
	public void engineUpdate(byte[] input, int offset, int len) {
		// make sure we don't exceed input's allocated size/length
		if (offset < 0 || len < 0 || (long) offset + len > input.length)
			throw new ArrayIndexOutOfBoundsException();

		// compute number of bytes still unhashed; ie. present in buffer
		int bufferNdx = (int) (count % BLOCK_LENGTH);
		count += len; // update number of bytes
		int partLen = BLOCK_LENGTH - bufferNdx;
		int i = 0;
		if (len >= partLen) {
			System.arraycopy(input, offset, buffer, bufferNdx, partLen);

			transform(buffer, 0);

			for (i = partLen; i + BLOCK_LENGTH - 1 < len; i += BLOCK_LENGTH)
				transform(input, offset + i);
			bufferNdx = 0;
		}
		// buffer remaining input
		if (i < len)
			System.arraycopy(input, offset + i, buffer, bufferNdx, len - i);
	}

	/**
	 * Completes the hash computation by performing final operations such
	 * as padding. At the return of this engineDigest, the MD engine is
	 * reset.
	 *
	 * @return the array of bytes for the resulting hash value.
	 */
	public byte[] engineDigest() {
		// pad output to 56 mod 64; as RFC1320 puts it: congruent to 448 mod 512
		int bufferNdx = (int) (count % BLOCK_LENGTH);
		int padLen = (bufferNdx < 56) ? (56 - bufferNdx) : (120 - bufferNdx);

		// padding is alwas binary 1 followed by binary 0s
		byte[] tail = new byte[padLen + 8];
		tail[0] = (byte) 0x80;

		// append length before final transform:
		// save number of bits, casting the long to an array of 8 bytes
		// save low-order byte first.
		for (int i = 0; i < 8; i++)
			tail[padLen + i] = (byte) ((count * 8) >>> (8 * i));

		engineUpdate(tail, 0, tail.length);

		byte[] result = new byte[16];
		// cast this MD4's context (array of 4 ints) into an array of 16 bytes.
		for (int i = 0; i < 4; i++)
			for (int j = 0; j < 4; j++)
				result[i * 4 + j] = (byte) (context[i] >>> (8 * j));

		// reset the engine
		engineReset();
		return result;
	}

	// own methods
	//...........................................................................

	/**
	 *    MD4 basic transformation.
	 *    <p>
	 *    Transforms context based on 512 bits from input block starting
	 *    from the offset'th byte.
	 *
	 *    @param    block    input sub-array.
	 *    @param    offset    starting position of sub-array.
	 */
	private void transform(byte[] block, int offset) {

		// encodes 64 bytes from input block into an array of 16 32-bit
		// entities. Use A as a temp var.
		for (int i = 0; i < 16; i++)
			X[i] =
				(block[offset++] & 0xFF) | (block[offset++] & 0xFF)
					<< 8 | (block[offset++] & 0xFF)
					<< 16 | (block[offset++] & 0xFF)
					<< 24;

		int A = context[0];
		int B = context[1];
		int C = context[2];
		int D = context[3];

		A = FF(A, B, C, D, X[0], 3);
		D = FF(D, A, B, C, X[1], 7);
		C = FF(C, D, A, B, X[2], 11);
		B = FF(B, C, D, A, X[3], 19);
		A = FF(A, B, C, D, X[4], 3);
		D = FF(D, A, B, C, X[5], 7);
		C = FF(C, D, A, B, X[6], 11);
		B = FF(B, C, D, A, X[7], 19);
		A = FF(A, B, C, D, X[8], 3);
		D = FF(D, A, B, C, X[9], 7);
		C = FF(C, D, A, B, X[10], 11);
		B = FF(B, C, D, A, X[11], 19);
		A = FF(A, B, C, D, X[12], 3);
		D = FF(D, A, B, C, X[13], 7);
		C = FF(C, D, A, B, X[14], 11);
		B = FF(B, C, D, A, X[15], 19);

		A = GG(A, B, C, D, X[0], 3);
		D = GG(D, A, B, C, X[4], 5);
		C = GG(C, D, A, B, X[8], 9);
		B = GG(B, C, D, A, X[12], 13);
		A = GG(A, B, C, D, X[1], 3);
		D = GG(D, A, B, C, X[5], 5);
		C = GG(C, D, A, B, X[9], 9);
		B = GG(B, C, D, A, X[13], 13);
		A = GG(A, B, C, D, X[2], 3);
		D = GG(D, A, B, C, X[6], 5);
		C = GG(C, D, A, B, X[10], 9);
		B = GG(B, C, D, A, X[14], 13);
		A = GG(A, B, C, D, X[3], 3);
		D = GG(D, A, B, C, X[7], 5);
		C = GG(C, D, A, B, X[11], 9);
		B = GG(B, C, D, A, X[15], 13);

		A = HH(A, B, C, D, X[0], 3);
		D = HH(D, A, B, C, X[8], 9);
		C = HH(C, D, A, B, X[4], 11);
		B = HH(B, C, D, A, X[12], 15);
		A = HH(A, B, C, D, X[2], 3);
		D = HH(D, A, B, C, X[10], 9);
		C = HH(C, D, A, B, X[6], 11);
		B = HH(B, C, D, A, X[14], 15);
		A = HH(A, B, C, D, X[1], 3);
		D = HH(D, A, B, C, X[9], 9);
		C = HH(C, D, A, B, X[5], 11);
		B = HH(B, C, D, A, X[13], 15);
		A = HH(A, B, C, D, X[3], 3);
		D = HH(D, A, B, C, X[11], 9);
		C = HH(C, D, A, B, X[7], 11);
		B = HH(B, C, D, A, X[15], 15);

		context[0] += A;
		context[1] += B;
		context[2] += C;
		context[3] += D;
	}

	// The basic MD4 atomic functions.

	private int FF(int a, int b, int c, int d, int x, int s) {
		int t = a + ((b & c) | (~b & d)) + x;
		return t << s | t >>> (32 - s);
	}
	
	private int GG(int a, int b, int c, int d, int x, int s) {
		int t = a + ((b & (c | d)) | (c & d)) + x + 0x5A827999;
		return t << s | t >>> (32 - s);
	}
	
	private int HH(int a, int b, int c, int d, int x, int s) {
		int t = a + (b ^ c ^ d) + x + 0x6ED9EBA1;
		return t << s | t >>> (32 - s);
	}

	/**
	 * Bugfixed, now works prima (RST).
	 */
	public static int Com_BlockChecksum(byte[] buffer, int length) {
		
		int val;
		MD4 md4 = new MD4();

		md4.engineUpdate(buffer, 0, length);
		byte data[] = md4.engineDigest();		
		ByteBuffer bb = ByteBuffer.wrap(data);
		bb.order(ByteOrder.LITTLE_ENDIAN);
		val = bb.getInt() ^ bb.getInt() ^ bb.getInt() ^ bb.getInt();
		return val;
	}
}
